-LRB- CNN -RRB- -- The Pentagon says it 's `` ready to go '' if it gets orders to carry out a military strike in response to Syria 's suspected use of chemical weapons against its own people .

Most people know Syria 's civil war has been raging for more than two years . But the situation is so complicated that it 's hard for even the biggest news junkie to keep track .

Now that Washington is seriously thinking about ordering limited missile strikes in one of the most volatile regions of the world , it 's a good time to retrace events and remember how we got here .

Here 's a quick-read cheat sheet about the Syrian civil war . It 's not intended to be an all-encompassing encyclopedia , but it will bring you up to date on what 's really important about a scary situation in an already volatile part of the world .

Who wants what after chemical weapons horror ?

1 . What did Syria look like before the conflict ?

Even before the uprising in Syria , things were n't peaceful there . Discontent simmered for decades .

In 1982 , President Hafez al-Assad clamped down on a Muslim Brotherhood uprising . In one attack , his iron fist left tens of thousands dead .

When Hafez al-Assad died in 2000 , his son Bashar al-Assad took over the presidency . He promised to build a more modern and democratic nation .

But reforms did n't come fast enough for activists , who called for change and slammed Syria 's government as an `` authoritarian , totalitarian and cliquish regime . ''

Sectarian and ethnic unrest shook Syria over the past decade , too . A Druze uprising flared in 2000 , and a Kurdish rebellion erupted in 2004 .

2 . How did the civil war begin ?

It all started in February 2011 in the city of Daraa , when authorities arrested 15 schoolchildren for painting anti-government graffiti on the walls of a school . The children did n't mince words with the message they painted : `` The people want to topple the regime . ''

Word spread that the children were allegedly mistreated while in custody . Outrage over their arrest grew , fueling protests .

Security forces opened fire , activists say , killing at least four protesters .

These four , activists say , were the first deaths in Syria 's civil war .

Within days , according to Human Rights Watch , protests grew into massive rallies made up of thousands .

Their rallying cry : `` Daraa ! '' the city whose children sparked a national movement .

Iran : U.S. military action in Syria would spark ` disaster '

3 . How did the unrest turn into a call for an end to al-Assad 's rule ?

It did n't take long for al-Assad to criticize protesters in Daraa . In a March 2011 speech before lawmakers , he said `` conspirators '' started out there and wanted to spread unrest .

His dismissive remarks , and the way lawmakers applauded afterward , only further fueled protests .

`` That speech had a catastrophic impact , '' the International Crisis Group 's Peter Harling said last year . `` People who wanted to support the regime at the time were shocked . ''

Two days later , weekly anti-government protests began across Syria . Calls for reforms soon escalated into calls for the removal of the entire al-Assad regime .

Now , armed rebels have vowed to accept nothing less than al-Assad 's ouster , while the Syrian government has labeled them terrorists and vowed not to back down .

The United Nations estimates that the fighting has claimed more than 100,000 lives .

4 . OK , but that all started more than two years ago . Why do some people think the United States needs to take action now ?

Talking about Syria last year , President Barack Obama said `` a red line for us is , we start seeing a whole bunch of chemical weapons moving around or being utilized . ''

The implication was clear . If Syria uses chemical weapons in the civil war , the United States will have to do something .

Now , the White House says it looks like Syria has used chemical weapons against its own people . So here we are .

What will Obama do in response ? Whatever it is , it 's time to sit up and take notice , because this news story is moving to another level .

What justifies intervening if Syria uses chemical weapons ?

5 . What makes chemical weapons a game changer ?

Some argue that conventional weapons like guns or bombs also have a massive human toll . They say chemical weapons should n't be a turning point for the world to act .

But the White House maintains that they 're a game-changer .

`` The use of chemical weapons is contrary to the standards adopted by the vast majority of nations and international efforts since World War I to eliminate the use of such weapons . ... The use of these weapons on a mass scale and a threat of proliferation is a threat to our national interests and a concern to the entire world , '' White House spokesman Jay Carney said this week .

6 . Why did n't the United States just send a bunch of weapons to the opposition when it had the chance ?

In June , the United States said it would send the rebels small arms , ammunition and potentially anti-tank weapons . But that was long after the unrest started . Why the delay ?

Some argue that sending weapons to a region of the world that also contains Islamic extremists is risky business .

Many of the rebel fighters are militants with pro-al Qaeda sympathies , the same stripe of militants America has battled in Iraq and Afghanistan .

The Syria rebels have promised U.S. and European officials that any military weaponry they get wo n't end up in extremists ' hands . But that has n't quelled criticism from some quarters that arming the rebels is a dangerous risk .

Russian President Vladimir Putin has slammed the decision to arm the opposition . At an economic forum in June , he cautioned , `` Where will those weapons end up ? ''

7 . What 's the deal with Russia ? Why are they criticizing the U.S. ?

Putin has made it clear that Russia and the United States do n't see eye to eye when it comes to Syria .

Russia and Syria are longtime allies . For one , just take a look at their weapons deals . Between 2007 and 2010 , Russian firms selling weapons to Syria made almost $ 5 billion .

It would be costly for Russia to end that relationship , analyst Peter Fragiskatos said this year

`` Russia 's leadership still sees much to lose economically and strategically from cutting Syria loose , '' Fragiskatos wrote . `` Russia sees Syria as another test case for the West 's appetite for intervention and views the danger of U.S. involvement as a direct threat to its own interests . ''

There are other reasons to suspect that Russia will keep supporting Syria . Russia 's only naval base in the Mediterranean is on the Syrian coast , and Putin is still upset about NATO 's bombing in Libya two years ago that removed Russian ally Moammar Gadhafi from power .

` Red line ' debate : Chemical weapons worse than attacks ?

8 . What 's religion got to do with it ?

The al-Assad family is Alawite , a Shiite Muslim offshoot that 's one of the minorities in a country that is nearly three-quarters Sunni .

Al-Assad has filled key positions in his government with extended family members , and many of his supporters are Alawites and other minorities who fear what might happen if the Sunnis were to gain power .

Because the Syrian regime is Alawite and the majority of the country is Sunni , there are concerns that Syria could spiral into even more violence .

9 . What 's the worst that could happen ?

In a worst-case scenario , experts say , the fighting could spill over and make trouble for Syria 's neighbors , threatening stability in a part of the world that 's already known to be volatile .

Surrounding Syria are Lebanon , Iraq and Jordan , Israel and Turkey . The violence has been prompting war refugees to seek safety in some of these nations . In Turkey , there are ethnic tensions involving Kurds who live along its southern border with Syria .

All of these countries have a lot of religious , cultural and historical issues between them that add countless layers of complexity to the crisis . And when an entire region of the world loses stability , that worries the international community as a whole .

CNN 's Nic Robertson , Thom Patterson , Joe Sterling , Barbara Starr , Chelsea J. Carter and Kyle Almond contributed to this report .

@highlight

Unrest in Syria started after children were arrested for anti-government graffiti

@highlight

Outrage over arrests spiraled into protests that fueled an opposition movement

@highlight

The White House has said chemical weapons are a game changer

@highlight

Russia is standing by Syria , its longtime ally